Thanks, Tac - that picture is of the "as-acquired" state of the batteries, taken a couple of years ago. I thoroughly cleaned the connections long ago. The three way valve is to the water tank. Since I am 240 miles from the boat, I have been scrounging through my old photographs looking for ones that generally illustrate items, but overall the condition of most things is better than now than it looks in the pictures.

Thanks again, Tac and everyone who posted or even took the time to read this thread. I'm headed to the boat in a couple of days to work on the charging system and a whole lot else and will report back on how things work out. As always, the A4 formum has come through for me, and I am very grateful.